Fluorine-contained resins have excellent hardness, abrasion resistance, chemical resistance, solvent resistance, and weatherability. Because of these properties, which are very desirable to covering materials, fluorine-contained resins are extensively used as coating materials on various substrates.
However, fluorine-contained resins are defective in that since their adhesion to various substrates is poor, coating films formed by applying fluorine-contained resins on surfaces of various substrates are apt to peel off.
As expedients for improving the poor adhesion of fluorine-contained resins to, for example, metallic substrates, use of a composition, as a primer, comprising an epoxy-acrylate resin, a vinylidene fluoride resin, a methacrylate resin, etc. is disclosed in JP-A-1-149880 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and, further, use of a composition, as a primer, comprising a polyol resin, a polyisocyanate compound, and a thermoplastic acrylic resin as essential ingredients is disclosed in JP-A-1-146965.
Techniques of coating a fluorine-contained resin on substrates made of polyolefin resins represented by polyethylene and polypropylene, however, are still insufficient, and the defect that coating films formed are prone to peel off still remains unsolved.